Power outlets are in 220V/110V in houses for historical reasons (light bulbs and other appliances probably required >100V voltage) but nowadays as:

  • we use a USB charger 220V->5V for phones, tablets, ...
  • we use LED bulbs which probably work on low voltage
  • we use TV and computers that work on ~12V or ~20V after a power supply unit
  • many people use vaccuum cleaner and other appliances (drill) with batteries

are there any official standards (or drafts of future standards) for building houses with no 220V/110V outlets in bedrooms, bathrooms, etc. and only 220V/110V in kitchen and laundry room (for washing machines)?

Would it be possible to have one single 12V converter in the electrical panel, and no voltage outlet > 20V in, at least, bedrooms?

Note: this hypothesis is only valid in the case the house heating is not with electricity

  • 1
    \$\begingroup\$ You are asking for speculation (opinions). Asking for opinions are off topic. Your question body also shows a lack of research. \$\endgroup\$
    – Andy aka
    Mar 29, 2022 at 9:19
  • \$\begingroup\$ No @Andyaka, I'm not really asking for opinions, but if there are any standards or drafts of standards about this? I know that here in Europe building houses should meet very strict standards about electricity, so I'm curious if there is a standard about <20V bedrooms or a draft of future-coming standard about this. \$\endgroup\$
    – Basj
    Mar 29, 2022 at 9:27
  • 3
    \$\begingroup\$ It's technically not viable to run 12V in the house. The 12V is only used inside shower (or near it), othersiwe 220V is pretty safe (enough) in bedrooms. Try calculating the electric current needed for 2kW electric kettle at 12V, or other high-power appliances. Then imagine the length of wires inside the house and the losses over 20m+ of cables. Not even mentioning the lack of low-voltage-high-current electric outlets. \$\endgroup\$
    – akwky
    Mar 29, 2022 at 9:29
  • 1
    \$\begingroup\$ does it really still make sense to have potentially dangerous 220V/110V in bedrooms? - is asking for opinions - have you any evidence that there is a problem here that needs to be solved? \$\endgroup\$
    – Andy aka
    Mar 29, 2022 at 9:31
  • 1
    \$\begingroup\$ In a future (20 years from now?) in which a standard exists (let's say 5V or 12V for all electronic devices), would it be possible to have one single 12V converter in the electrical panel, and no voltage > 20V in, at least, bedrooms? = call for speculation. \$\endgroup\$
    – Andy aka
    Mar 29, 2022 at 9:55

1 Answer 1


There's more to consider than the voltage level needed by the devices typically connected to an outlet.

  1. Having a wall outlet implies that the devices to be plugged into aren't predetermined. E.g. you will have to operate a vacuum cleaner in every room except you live in a slaughterhouse where you can clean everything using a waterhose. A very modern vacuum cleaner could operate with only 500 W and could limit inrush currents effectively as they have inverters built in anyway. However this device needed 40 A to do its job, difficult to supply that over any user operable connection.

  2. Using such high DC currents is a bad choice, because arcing can be serious when disconnecting

  3. Voltage drop on the wiring of the house increases by a great portion. It is proportional to the current and as we saw at 1) current increases when lowering the voltage at constant power output

  4. Even if we increased the wire diameter to keep the voltage drop constant we would loose much more energy because the usable portion of the voltage of our home grid will be much smaller relatively to the voltage drop.

  5. Outwhitting that by further increasing the wire diameters will attract only copper thieves.

The vacuum cleaner is only the most descriptive example. When thinking over it, you will find even more devices which have to be used at changing places demanding much power.

  1. Having rooms with 110/220 V and rooms with 12V (or other SELV) will burden you with managing and servicing two separate grids. Cost for installation and maintenance could easily double.

  2. Most likely in such homes the 110/220 V will coexist in most rooms with the 12 V grid. You may claim that if in a substantial portion of cases the safe 12 V will be used reducing the chance to get in contact with the "dangerous" 110/220 V. This may be hampered by multiple possibilites for both grids connected to each other by accident. Furthermore a rarely used system is more prone to receive bad maintenance leading to increased failure rate.

Summary: The typical power consumption profile of household appliances with changing location will effectively prevent the change to an at least partially exclusive SELV-grid in homes.

  • \$\begingroup\$ Thanks! Just for future reference: how much thicker would the wires have to be if we want to support, say 500W? \$\endgroup\$
    – Basj
    Mar 29, 2022 at 9:47
  • 1
    \$\begingroup\$ @Basj The wire diameter needs to go as the square of the current. So it you use 1mm2 wire at 240 V (which will run about 10 A), you'll need (240/12)^2 = 400 mm2 for the same losses at the same power use. Now do you realise why there hasn't been a rush to wire houses for 12 V. It's bad enough wiring a small RV for 12 V. Ok, perhaps only 100 mm2 for 500 W. \$\endgroup\$
    – Neil_UK
    Mar 29, 2022 at 9:53
  • \$\begingroup\$ @Neil_UK Ok I see, this is probably the number 1 reason then! multicoquespratique.fr/pages/entretien-et-maintenance/… \$\endgroup\$
    – Basj
    Mar 29, 2022 at 9:58

Not the answer you're looking for? Browse other questions tagged or ask your own question.